Two-Filter Printing on Variable-Contrast Papers

By David Vestal Back to

In the January/February 2009 issue of PHOTO Techniques, Dick Dickerson and Silvia Zawadzky correctly said and showed that printing with two contrast filters— a low-contrast one such as Ilford’s #00 and a high-contrast one such as Ilford’s #5—will not give us “richer” black-and-white prints than printing with any one of the contrast f ilters provided by Ilford, Kodak, and other manufacturers, or with no filter.

They then concluded, not altogether correctly, that split-filter printing “does not afford access to a print appearance (contrast, curve shape) unattainable with single filters; it just takes longer to get there.”

Intermediate grades

In saying this, they overlooked one limitation of the manufacturers’ filter sets. The filters are designed to produce 12 distinct degrees of contrast, spaced half a contrast grade apart, from softest (lowest contrast) to hardest (highest contrast). The results per filter vary somewhat when we use different papers and/or different paper developers, but with any such combination we are locked into those 12 degrees of contrast when we use those f ilter sets, or the grade numbers furnished by enlargers with built-in filtration, one filter or setting at a time.

Incidentally, I have tested contrast filter sets sensitometrically, and have never found one that gave consistent or accurate half-grade differences from one filter to the next. The Kodak and Ilford sets that I’ve used are def initely quite uneven. Don’t worry about this; there’s nothing we can do about it. Also, gelatin contrast filters, which I use above the lens in my old but good Omega D2V enlarger, fade over time, as I learned one day when I saw that my #31/2 filter was giving me higher contrast than my #41/2, which had faded more. It was time to get a new set.

Once in a while, we want to make a straight, unmanipulated print with contrast that falls between that furnished by either of two adjacent single filters. For instance, if we want a print that is softer than #3 but more contrasty than #21/2, we can get to about grade 23/4 by giving half the print’s exposure with the #21/2 filter and half with the #3. It doesn’t matter which filter comes first. Yes, this takes longer than single-filter printing, but it does give us a print that we can’t get with any single f ilter. What makes Dick and Silvia almost absolutely right is that such fine contrast-distinctions in prints are barely perceptible to the eye. In general we don’t readily see contrast differences of less than 1/4 grade in picture prints.

I do not mean to scold Dick and Silvia: I believe they give the most accurate information on black-and- white technical matters available in any magazine. In most such matters I trust them more than I trust myself, because they know more than I do, and because they are honest.

Masks and filters

With some problem photos in which the light and dark shapes are so intertwined that dodging and burning-in aren’t practical, I know of two ways to get to a good print. One is to make a mask and print through a negative-and-mask sandwich. Al Weber knows exactly how to do this, but I have never learned it, so I use a two-filter method, which I find easier, although I think it must be a little less effective than masking. Still, it helps.

This consists of printing with only the softest and the hardest filters. The method goes like this. Make test strips or prints to f ind the minimum print exposure with the soft filter that gives you distinct tones in the picture’s “whites” (light grays that say “white” but show detail). Then make more tests that combine that soft-filter exposure with different amounts of hard-filter exposure to find the hard- filter exposure that, when added to the soft exposure, pumps up the picture’s darkest grays to give good “blacks” (dark grays that say “black” but show detail). This gave me a decent print of a produce market in Salvador-Bahia, Brazil, shot from some distance, that shows black people in white clothes in both sun and shade, and gleaming metal oil tanks in bright sunlight on a hill above the market. The first print

was too dark to suit me, but the proportion of soft exposure to hard exposure gave just the contrast I wanted. I then used a pocket calculator to find 9/10 of the soft exposure time and 9/10 of the hard one, and giving those 9/10 exposures did the job. A different percentage change in each would have given me a lighter or darker print of the same contrast, but that wasn’t necessary this time.

The point is that, although one filter that gave the exact degree of contrast that this photo needed would have done the job as well and more easily, I didn’t know what degree of contrast that might be. I tried two or three single filters, none of which was right. Fiddling with #00 and #5 took some more time but delivered the degree of contrast that worked for me in prints.

Fortunately, this is seldom needed. I’m almost sure that masking can solve contrast problems better than two-filter printing can, but they both work. And just imagine what you could do by using both. It would take time, but we all have 24 hours every day, and it would be interesting.

Fixing white skies

There is another use for two-filter printing. A common case is the landscape with dark ground and a bright sky. When the dark ground is printed through a f ilter that gives it lively contrast among its dark tones, the sky prints far too light. It stays blank white. (Some students call that “blown out.”) It’s a useful common practice to burn-in the sky through a soft f ilter, before or after the main exposure for the ground, until we get a print that shows our white clouds and open sky in full detail. In prints, because of the paper’s curve, all very light tones are inevitably low in contrast, so the softest filter can’t degrade them much and offers more latitude than contrastier filters. A double-zero-filter burn also doesn’t show so much when our sky-burn overlaps the area of darker ground, so there is no unwanted black edge at the top of the ground.

It’s useful to know that the human eye sees differences in light tones much more distinctly than it sees equal differences in dark tones. To see this, just examine a Kodak gray-scale strip; its 21 steps range from white to black in evenly differentiated tones, the measured densities of which plot in a straight line on graph paper.

Or if the sky is bigger in the picture than the ground, it makes sense to expose the print to show sky tones as well as possible, while dodging to keep the ground from printing too dark. If dodging the ground is no good because its tones are too low in contrast, you can dodge the ground with a contrasty gelatin f ilter instead of using cardboard. This both lightens the ground and gives it higher contrast. It took me only 40 years of printing to think of this simple thing.

Ilford or Kodak 6×6-inch f ilters make this easy. Those two f ilter sets look different, but they behave very much alike. In 1985, when I visited an Ilford factory in England, I was told that Ilford was then making Polycontrast f ilters for Kodak as well as their own Ilford filters.

To sum this up, printing with two contrast f ilters can be useful in several ways, although using only one filter, or none, is just as good, or better, for most black-and-white photos.

I like to do things as simply as I can and still get good results. This is a matter of temperament. Some good photographers choose to work in difficult and complicated ways. One whom I knew, Leo Stashin, felt sure that he had to use all 12 contrast filters in making every print. He told me his mystical reasons why he needed each filter for a certain elusive and necessary quality that it alone could give. He always needed them all. And his prints were excellent.

So cheer up and work the right way, which means, just as you please.


About the Author

David Vestal
Dvestal
David Vestal is a photographer and teacher whose publications include The Art of Black & White Enlarging (1984) and The Craft of Photography. His photographs are exhibited internationally and are found in numerous private and public collections including New York City’s Museum of Modern Art and the George Eastman House in Rochester, NY. The wit and wisdom of his commentaries have long earned him a strong following among readers.